1. Field of the Invention
This invention relates generally to methods and apparatus for identifying broadcast programs and particularly to the automatic identification and reporting of broadcast performances of musical works, commercials and the like.
2. Discussion of the Related Art
The broadcast industry requires accurate monitoring and reporting of broadcast programming for a variety of economic purposes. Advertising revenues are often computed as a direct function of audience numbers estimated by means of broadcast program monitoring systems. Commercial advertising revenue also depends on the number of commercial repetitions and the precise commercial broadcast day, hour and minute. Licensing revenues are computed based on the number of broadcast performances of the underlying work, such as a musical recording, movie or syndicated feature program.
There are many systems known in the art for identifying and verifying the broadcast performances of various works, whether commercials, musical works or feature works. These systems can be broadly characterized as manual and automated.
Manual monitoring and reporting systems require human operators to review recorded broadcast signals, to recognize and identify each broadcast performance and to log the work identification and the broadcast date and time. Even with the assistance of computer-implemented logging and reporting systems, such manual monitoring schemes are labor-intensive and therefore very expensive to operate. Moreover, reliance on manual techniques introduces an uncontrollable source of error in the resulting broadcast performance reports.
Automated monitoring and reporting systems for broadcast programming can be broadly characterized as cooperative and unilateral. Cooperative electronic monitoring systems rely on special coding signals embedded in the broadcast programming for accurate recognition and identification of individual works.
Cooperative systems that detect identification signals embedded in the broadcast signal require the cooperation of the broadcasters, who must encode the broadcast of each program for such systems to be effective. Because of financial conflicts-of-interest between the broadcaster and the advertiser or licensor, any cooperative monitoring and reporting system that relies on broadcaster cooperation introduces uncontrollable credibility problems in the monitoring reports.
In U.S. Pat. No. 4,857,999, Russell J. Welsh discloses a broadcast commercial monitoring system that identifies commercials by detecting closed-caption characters and extracting identifiable signatures therefrom. Welsh's system is intended to verify commercial broadcast frequency for advertising billing purposes and relies on the closed-caption signal for the hearing-impaired that is embedded in the commercial for purposes other than cooperative broadcast monitoring. Because this embedded signal is easily decoded into a series of digital characters, Welsh's system provides accurate identification without extensive computational effort. However, Welsh neither considers nor discusses the problem of identifying performances of musical works or the like that do not include such embedded signals.
In recent years, completely automatic unilateral broadcast signal identification systems have been disclosed that require no special coding of the broadcast signal. These unilateral monitoring systems rely on signal processing techniques to extract a "signature" from the broadcast signal for use in identification of the broadcast work by comparing it to a predetermined library of signatures.
For instance, in U.S. Pat. No. 3,810,156, Robert N. Goldman discloses a signal identification system that uses a concise digital "signature" developed by accumulating several broadcast signal samples. Although Goldman's system does not require embedded code signals, he merely suggests converting each two seconds of broadcast signal into a single digital number and neither considers nor suggests techniques for overcoming the inherent inaccuracies of such a technique, preferring to rely on the supposed benefits of aggregation over many samples.
In U.S. Pat. No. 4,739,398, William L. Thomas et al. discloses a system for recognizing broadcast segments such as commercials by applying continuous pattern recognition to signals derived from the broadcast signal representing strategically-selected regions of each video frame. Similarly to Goldman. Thomas et al. extract a signature using a parameter mask and consult a library for comparison and identification. They do not suggest means for overcoming the inherent inaccuracies of such comparison methods introduced by errors arising from mismatched timing, loss of synchronization and random noise.
In U.S. Pat. No. 4,450,531, Stephen C. Kenyon et al. disclose a broadcast signal recognition system and method that obtains signal correlation of a plurality of reference and broadcast signal segments. Kenyon et al. teach that signal disturbances such as noise bursts or dropout can be overcome by relying on a test for coincidence between many separate signal portions and reference signals. However, Kenyon et al. require very substantial signal processing resources to handle the multiple cross-correlations of broadcast signal segments required for their technique, and do not suggest effective means for overcoming problems introduced by program truncation and timing errors.
In U.S. Pat. No. 4,230,990, John G. Lert, Jr. et al. disclose a broadcast program identification system that extracts signatures responsive to either a natural or inserted "cue" and then compares the signature with a large library for identification. In U.S. Pat. No. 4,677,466, Lert et al. improve on the earlier identification system by extracting a signature responsive to a finding of "stability" in the signal as determined by comparing "events" in sequence. These events include such things as the signal blanking indicating a switch to commercial and the like. Their system is disclosed as shown in FIG. 1 herein where the improvement is the comparison of subsequent events to determine a stability condition, thereby eliminating the requirement for embedded cues. In U.S. Pat. No. 4,697,209, David A. Kiewit et al. disclose the application of the Lert, Jr. et al. technique to in-home monitoring of television viewer activity by means of a local system that monitors all program viewing in the home, whether received via broadcast or produced in a local video cassette player. Neither Lert et al. nor Kiewit et al. suggest how to overcome the inherent inaccuracies of their methods arising from errors introduced in the broadcast signal that hinder accurate comparison of other "signatures" with the corresponding library reference signals.
Single and multiple reference segment signal identification systems can theoretically operate effectively where ideal signal conditions prevail, but such systems are relatively ineffective under typical broadcast operational conditions. For example, with intermittent signal dropout, a single segment correlation may be severely degraded and thereby result in failure to indicate correspondence of the broadcast and reference signals when correspondence does in fact exist. Measures intended to accommodate such intermittent errors can introduce unacceptable levels of "false" identification of the target work.
With broadcast music programs, speed variations between the same musical work played by different broadcast stations may be so extreme that even the use of sub-audio techniques known in the art for single reference segment systems give inadequate performance. Known broadcast signal identification systems cannot cope effectively with substantial music speed variations. It has been found that disk jockeys, to create desired effect, are quite likely to vary recording playback speeds to control playback duration time and to segue into and out of a popular musical work, thereby omitting portions of the recording at the beginning and end. Even under ideal conditions, signal processing methods that rely on simple linear cross-correlation techniques introduce high "false alarm" identification rates that reduce overall monitoring and logging system performance to less than 60% effectiveness. Even the most effective of such systems requires enormous processing power and very large signature library storage capacity, thereby making such systems disadvantageously expensive.
Accordingly, there is a clearly-felt need in the art for a broadcast performance monitoring and reporting system that can provide reports of the time and date of actual broadcast performances of identified works, such as recorded music, commercials and the like with substantially improved effectiveness at substantially reduced cost. The related unresolved problems and deficiencies are clearly felt in the art and are solved by our invention in the manner described below.